Hi Sam,

My name is Graham and this is my first post, but as I do know a bit about the subject, thought I'd reply (although 10 months later).

I've ridden the NSR in anger (quite a while ago), and currently have an 1984 NS that I restored in Rothmans Colours - I ride this as often as I can in the local hills (Brisbane, Australia). The NS250R and NSR250 are very different bikes, and a good rider will be able to go (almost) just as well on either. Though I do believe it is hard to ride hard on the NS - you really do have to be on your 'A' game to get the most out of it, but when you do, it is worth it.

The NSR (and other later two-strokes like KR1 and RGV) seem to work better outside of the powerband (i.e. lower in the rev range). They will get you to the hills or track more comfortably then the NS will. In this I mean that the Power Valves (or equivalent) do a good job in providing low down power, so that every time you take off from the lights you do not need to be 'gunning' it to get going (you still have to rev, but not as frantic). This makes them easier to ride outside of their design parameters.

The NS, on the other hand, has very little below 7,000 revs, a little above this, and then a lot from 8,000 to 10,500 revs (the powerband). To me, this makes it a Jekyll and Hyde bike. Get beaten by almost everybody in the suburbs, but then hit the hills and it seems you are on a different bike. The ATAC system just does not compare to later powervalves.

If you are looking for parts, I'd suggest first to visit Ian Wright's Classic Replicas, or other sites like Mega Zip Parts and CMSNL Parts.

Hope this assists.
Cheers.